Synthesis And Characterization Of Multi-armed CdS Nanorod And The Photovoltaic Characteristic Of CdS/PVK Composite System

Nanocomposites consisting of multi-armed nanorods and a good hole-transporting polymer, such as poly (N-vinyl carbazole) (PVK) promised both the large interface for the separation of charge and the efficient one-dimensional electrical transport. This nanocomposites also solved the problem that one dimensional ordinary nanorods have no contribution to the lengthways transport of electrons because the nanorods mainly lay horizontally in the films when they were formed compositefilms. So they have an important meaning for enhancing efficiency of the separation of charge at the interface, the transportation and collection of charge carriers. So they have shown promise for photorefractive applications, lightemitting diodes, and photovoltaic devices.First, CdS is an important photoelectric semiconductor material. CdS nanorods were successfully synthesized in bulk quantities through Cd(CH₃COO)₂·2H₂O reacting with Na₂S-9H₂O and ethylenediamine in aqueous solution. XRD result shows the sample is hexagonal CdS, and TEM result displays the resulting CdS are three-armed rod-like morphology with diameters of 10～15 nm and lengths of ca. 100 nm. We also discussed the optical and photoelectric properties of three-armed CdS nanorods by photoluminescence and surface photovoltage spectroscopy. This nanorods have special structure because they can afford much more passages for the transport of electron and effectively enhance the ability of the charge transfer. Consequently they are propitious to the separation of electron-hole pares.Then, we present here the results of a charge carrier mobility study in a system comprised of cadmium sulfide nanorods (QCdS) dispersed in poly(N-vinyl carbazole)(PVK).The nanocomposite films of CdS/PVK were prepared by spin coating method on the substrate of ITO glass, with 3000 cycles per minute and then the filmswere dried in the air. We investigate the photoelectric character characterization ofCdS/PVK nanocomposite films through photoluminescence and surface photovoltagespectroscopy. The results show that photoluminescence efficiency of PVK decreasesand have significant enhancement in photovoltage signal when the molar fraction ofCdS increases. The phenomenon of the quenching of photoluminescence and theincreasement of the SPS value indicates that interfacial electron transfer occurs betweenthe CdS nanoparticles and the PVK molecules. Such an interfacial charge transferbrings down the recombination probability of electrons and holes, and thus increases thelifetime of the holes in the HOMO of PVK and electron in CdS. As a result, the chargecarriers have more chances to migrate to the preper electrode and the photoelectrictransfer efficiency of the nanocomposite increases. And we also discussed the detailedprocess of the charge transfer occurred at the interface of CdS and PVK. They providetheoretical and experimental basis for developing new high performance photoelectricdevices.